Quality control: Inspection schedule
In NI, your local authority will arrange a set number of mandatory inspections for your build. You will have to notify your building control officer when they are to call on site. You can also ask them to call out when you feel necessary to check work you are unsure about is being carried out in compliance with the building regulations; they will do their best to accommodate such additional requests.
Remember that their role is to check compliance with the regulations, anything outside of this is not within their remit. Some officers will be used to working with certain methods and materials and if you are using unusual techniques, the input of a professional architectural designer will be especially useful to consult with the building control officer on site. The only cost to you are the statutory application fees.